Quarterly report pursuant to Section 13 or 15(d)

Real Estate Variable Interest Entities (Details)

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Real Estate Variable Interest Entities (Details) (USD $)
In Millions, unless otherwise specified
0 Months Ended 0 Months Ended
Jun. 15, 2011
Jun. 15, 2011
Six Fifty North Glebe Road [Member]
Jun. 30, 2012
Six Fifty North Glebe Road [Member]
Dec. 31, 2011
Six Fifty North Glebe Road [Member]
Nov. 23, 2011
Braddock Gateway [Member]
Jun. 30, 2012
Braddock Gateway [Member]
Dec. 31, 2011
Braddock Gateway [Member]
Real Estate Properties [Line Items]              
Estimated development costs   $ 45.0     $ 95.3    
Percentage of capital contribution through debt 70.00% 70.00%     70.00%    
Variable interest entity, qualitative or quantitative information, ownership percentage   90.00%     95.00%    
Percentage of residential property to be leased to achieve project stabilization stage   90.00%          
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners   10.00%     5.00%    
Land and capitalized development costs related to joint ventures     14.5 13.4   16.0 14.4
Accounts payable and accrued liabilities related to joint ventures     $ 0.3 $ 0.1   $ 0.4 $ 0.2